JPH0328839B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser device made according to the gas transport or convection principle, with a gas circulation system and an excitation system.

The power, amplification and efficiency of molecular lasers, especially _CO2 -lasers, decrease with increasing temperature of the laser gas. The reduction in possible power is due to the increase in temperature, which increases the width of the lines, the excitation energy is distributed over an increasing number of circulating lines, and the number of deactivated collisions increases,
It is based on the increased occupation of the laser level by thermal excitation and the resulting reduction of the individual transition conversions.
(K. Gu¨rs, Laser 75, Optoelectronics, Conference Proceedings, 30~
37 pages).

For this reason, methods have been developed to remove heat from the laser gas by circulating and cooling the gas. Suitable lasers have adjacent or grouped optical resonators and consist of an active region in which the gas is excited and a gas introduction system including a cooler and a pump. Since a large amount of heat is dissipated, a large amount of gas must be circulated with a pump. Corresponding lasers are large and expensive, which limits their range of use.

All commercially available CO2 _- lasers with a power above 1 kW operate on the principle of gas transport or convection lasers. It was first described in 1969 by Teifanyi, Targ and Foster (Appl. Phys. Letters 15, 91-95).

Conventional gas transport lasers use gas delivery devices such as ventilators or Roots pumps for rapid gas circulation. There are differences between cross-flow lasers and axial-flow lasers depending on how the laser resonator is arranged and the direction of gas conduction. Both have their own strengths and weaknesses. In cross-flow lasers, pressure loss is relatively small due to the large flow cross section. Therefore, the required flow rate can be maintained with a smaller air delivery device than in the case of an axial laser.
However, this type of laser has difficulty achieving uniform discharge and emission in the reference mode. For this reason, the radiation of axial lasers should generally be focused.

In a convection laser, a gas flow is conducted in the axial direction through a glass tube that serves as a discharge vessel, and because the gas discharge conditions are radially symmetrical, better quality radiation is obtained and the radiation is well focused. Can be matched. Sufficient flow rate is maintained only if there is a relatively high pressure drop across the laser tube. Therefore, the discharge conditions along the tube are not uniform. Strong and weak air supply devices (roots pumps) are required.

Improvements in axial convection lasers are published in West German Patent Publication
2916408. In this embodiment,
The gas mixture circulates through a water-cooled conductor plate on a helical path adapted to fit inside the discharge vessel. It then passes through the active zone of the laser for only a short time and has enough time to dissipate the lost heat before the next cycle.
The spiral conductive plate has holes drilled in a straight line. Gas discharge for laser mixed gas excitation is performed through this hole. This device requires only relatively low circulation speeds and has the advantage of good modality due to the vertical arrangement of the laser resonator. However, it is difficult to maintain the gas discharge in one place because the gas discharge is easily blown out of the resonator space by the gas flow. The intensity of this laser type cannot be well controlled, since favorable operating conditions can only be maintained for very specific discharge parameters.

The object of the invention is to develop a gas transport or convection laser that can effectively suppress the temperature rise of the laser gas and maintain the required flow rate without expensive components in order to generate high-power laser radiation. be.

It has been shown that this problem can be solved by a laser device that is divided into parts with limited laser functionality, each of which is completely integrated. Embodiments corresponding to such an axial laser are described in claims 2 to 12.

The laser device proposed by the invention allows substantially high flow rates of laser gas. Correspondingly more heat is released together with the laser gas, so that for the same magnitude the laser power increases compared to the circulation speed. Output volume and velocity are reduced by 3-5 factors.

In the device according to the invention, for example, the component that moves the gas is no longer identified as a pump. First, the need for lasers is fully taken into account and new technology is introduced.

Next, embodiments of the present invention will be explained in detail based on the drawings. The drawings are shown schematically.

The device of the invention, as shown in FIG. 1, consists of a water-cooled central discharge tube 1 surrounded by a coaxial turbine air supply. The stator blades 2 of the turbine are firmly connected to the outer wall of the discharge vessel 1, thereby providing good cooling. The rotor blade 3 is fixed in a turbine tube 4 surrounded by two ball bearings 5 from the outside. A ring magnet 6 is provided between the ball bearings 5, and this magnet rotates the turbine rotor by the rotating magnetic field of the corresponding motor stator 7.

The laser space is closed by a thin-walled casing 8 in the turbine drive area such that only a small slit between the motor stator 7 and the rotor is effective. The case 8 is firmly connected to the end plates 9,10. Two mirrors 11 and 12 forming a laser resonator are mounted in the end plates 9 and 10 in an adjustable and gas-tight manner.

In another embodiment of the laser case, the turbine tube 4 can be fitted into the case, eliminating the rotor and stator walls. It is also possible to form the turbine tube 4 at the same time as the outer wall of the gas chamber and to place the bearings and rotor magnets in the outer chamber. The sealing of the turbine tube 4 to the end plates 9 and 10 takes place with slide seals. Such sliding packing is conveniently carried out using a magnetic liquid, such as an oil containing finely dispersed magnetic material. The packing element consists of a ring magnet with a U-shaped groove that retains the magnetic liquid and is located within the end plate.
The end of the turbine tube 4 is immersed in this groove without being in direct contact. The advantage of such a seal is the low friction and long life of the sealing effect.

If laser gas also exists in the external space and only a small amount of gas is exchanged with the external space, the turbine pipe and stator pipe (laser pipe) can fulfill the function of a laser gas introduction system even without packing. In the case of small grooves, the sliding gasket can be omitted, but in any case an outer casing must be provided, which connects the end plates 9 and 10 and surrounds the circulation turbine.

The gas circulation path is very short due to the compact arrangement of the laser tube 4 and the circulation system. Heat dissipation from the laser gas takes place very effectively in the circulation turbine, since the stator blades 2 are directly cooled. Since the gas flow is diverted in the shortest path in the two end plates 9 and 10, there are virtually no unused gas conduction sections as in conventional convection lasers.

A gas discharge takes place between electrodes 13 and 14. For insulation reasons, the inner wall of the discharge vessel 1 is made of ceramic. An operating voltage is applied to the electrode 14. Electrode 13 is at ground potential. The distance between the electrodes is set in proportion to the total length of the discharge tube 1, so that on the one hand the discharge voltage is minimized and on the other hand complete deactivation of the excited gas molecules is achieved during the flow of the flow space after the excitation zone. make sure that you are

The direction of the laser gas flow is changed using the end plate 9 or 1.
This is done by means of a turning section 15 which is created in the middle of the road. An electrode 1 is placed inside the discharge tube 1 shown in FIG.
3 and 14, the gas redirection section is formed in such a way that it connects the two ring-shaped openings of the turbine tube 4 with the central discharge tube.

Other embodiments of the laser concern modification of the gas discharge electrode or redirection section, as shown schematically in FIG. In this figure, a plurality of holes 16 are provided around the end plate 10 on the gas introduction side of the discharge tube, and a rod electrode 1 is provided with an insulating tube 17 in the hole 16.
8 is inserted. The deflection section 15 is subdivided within this region, and the laser gas flows through a plurality of holes in the laser tube 1, whose entire length serves as a flow space. A discharge is excited between each of the rod electrodes 18 and the wall of the hole 16. The advantage of this device is that the entire laser tube can be made of metal. The excitation and resonance chambers of the laser are strictly separated to optimize advantageous operating parameters.

The individual laser sections act as lasers, as already shown in FIGS. 1 and 2. The output power obtained is between 100 and 500 watts, depending on the size of the part.
In order to obtain outputs in the kilowatt range, both the suction and pressure sides are in each case flanged and connected in one example, as shown in FIG. 1 to 1, depending on the number and design of the laser sections configured in this way.
It can produce an output of 10 kilowatts or more.

The activation of the individual turbine rotors then takes place by means of a motor 19 via a shaft 20 parallel to the laser, as shown in FIG. A transmission belt 21 runs from this shaft to the turbine rotor 4.

In the embodiment shown in FIG. 5, the laser gas moves through a rotor section 22 having radially disposed wings 23. In the embodiment shown in FIG. The rotor 22 covers a wide area inside the case 24. The rotor blades 23 extend on the one hand to the housing wall and on the other hand to an excitation system 25 arranged along the housing wall.

The case wall has a cooling lip 27 from the outside for better cooling of the laser gas. This cooling lip 27 is mounted perpendicularly to the rotor axis and extends in the direction of laser gas flow.

As can be seen in FIG. 6, the excitation system here consists of a row of discharge chambers 28 with a central electrode 29 and a ring-shaped outer electrode 30. Moved by rotor 22, the cooled laser gas flows toward the excitation within the optical resonator where it radiates its excitation energy into laser vibrations. Instead of a simple spherical laser mirror 31, a refracting radiation mirror system can also be used.

The discharge chambers 28 arranged in parallel are fixed to the holder 32 (or directly to the case wall), the ends of which are shaped in accordance with the aerodynamic principle of flow. To prevent possible turbulence of the laser gas,
The rotor blades 23 ensure effective cooling of the laser gas because it has cuts or cavities that trap the gas between the cooling lips and allow the laser gas to move there. A possible embodiment of the rotor blade is revealed in FIG.

This circulation condition and cooling are achieved by making the rotor 22 hollow, and introducing the laser gas into the internal space of the case through a small hole 33 in the rotor, as shown in FIG. Further improvements can be made by re-releasing the
The laser gas exiting the case is then returned axially into the rotor 22. This circulation is maintained by centrifugal force and requires no pumps.

A possible variant of the laser arrangement according to the invention is to build the excitation system 25 in two or more rows of discharge chambers. When there are two rows of discharge chambers, for example, they are provided facing the case wall, and the rotor rotates between the two rows. In such embodiments, a case whose cross section is oval is preferred.
The discharge chamber is arranged on the side of the main shaft, so that the rotor blades can always adjoin the cooled case wall on the side of the countershaft.

The laser system according to the invention is, for example, 1 m long. The total cross-sectional area of the discharge chamber is 0.05 ^m2 . The flow velocity within the discharge chamber can be up to 160 m/s. This means that a gas volume of 8 m ³ /s flows through the discharge chamber. The composition of a suitable gas mixture is _CO2 :
_N2 :He=1:7:3. A convenient pressure range is from 50 to several 100 Torr. Under these conditions a system with an inner case length of 1 m provides a power output of 8 kW.
When there are two rows of discharge chambers, increase the size of the system,
Furthermore, when multiple systems are connected in series, a larger output can be obtained.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a laser device based on the axial flow principle of the present invention, FIG. 2 is a partially cutaway sectional view showing a possible arrangement of the laser electrode shown in FIG. 1, and FIG. 4 is an illustration of the driving configuration of the circulating turbine of the device of FIG. 3; FIG. 5 is a cross-sectional view of the laser device of the invention and a possible configuration based on the cross-flow principle. Front view, No. 6
The figure is a longitudinal sectional view of the embodiment shown in FIG. 5. 1...discharge tube, laser chamber, 2...stator blade,
3... Rotor blade, 4... Turbine tube, 5... Bearing, 6... Ring magnet, 7... Motor stator, 8... Case, 9, 10... End plate, 1
1, 12... Mirror, 13, 14... Electrode, 15...
Direction change section, 16... Hole, 17... Insulating layer, 1
8... Rod electrode, 19... Motor, 21... Conduction belt, 25... Excitation system, 26... Case wall, 28
...discharge chamber, 29 ... central electrode, 30 ... external electrode, 31 ... laser mirror.

Claims (1)

[Claims] 1. It is divided into parts with limited laser functions, each function is completely integrated, and the electrode is provided in the laser chamber or in the gas flow direction in front of the laser chamber, and the laser chamber is used as a cooling pipe. Laser device made according to the gas transport or convection principle, with a case containing a gas circulation and excitation system, characterized in that it is made and arranged concentrically in a circulation turbine. 2. Device according to claim 1, characterized in that the stator blades (2) of the circulation turbine are connected to the outer wall of the laser chamber (1). 3 The laser chamber 1 and the circulation turbine 4 are connected to the end plates 9, 10
3. Device according to claim 1, characterized in that the end plates (9, 10) are closed with a deflection section (15) inside the end plates (9, 10). 4. Any one of claims 1 to 3, characterized in that a magnet 6, for example a ring magnet, is provided to drive the turbine rotor by the rotating magnetic field of the motor. The device described in. 5. Any one of claims 1 to 4, characterized in that the turbine rotor is rotatably arranged inside a cylindrical case 8, and the case 8 extends between end plates 9 and 10. The device described in Crab. 6. The device according to any one of claims 1 to 4, characterized in that the turbine rotor is rotatably disposed within the end plates 9, 10, and the bearing is sealed with a slide gasket. 7. The device according to claim 6, wherein the slide gasket is made of a magnetic liquid and is inserted into and held by a magnet having a U-shaped cross section. 8 The inner wall of the laser chamber 1 is made of an insulating material, the electrode 13 on the gas introduction side is at ground potential, and the other electrode 14 is at ground potential.
8. A device according to any one of claims 1 to 7, characterized in that the electrodes are at the operating potential at regular intervals from the first electrode. 9 The spacing between the two electrodes 13, 14 is adjusted in proportion to the total length of the laser chamber 1, so that on the one hand a minimum discharge voltage is required and on the other hand the excitation gas is completely removed after leaving the excitation zone of the radiation field of the laser. 9. Device according to claim 8, characterized in that it is made inert. 10 A plurality of rod electrodes 18 at an operating potential around the end plate 10 on the gas introduction side are provided in the hole 16 and
6 , the gas flows into the laser chamber 1 through the hole 16 , the wall of the hole serving as an electrode. The device according to any of paragraph 7. 11. The device according to any one of claims 1 to 10, wherein the plurality of laser devices are connected to the suction side and the pressure side. 12 The circulation turbines of all laser devices are driven by a motor 19 with an axis 20 running parallel to the laser.
12. The device according to claim 11, characterized in that it is carried out via a toothed belt (21) running over the outer sleeve of the respective turbines.